Ratings boards aren't always consistent, for example I'll never understand why the first Genji game on PS2 got an M rating when the violence was neither bloody nor graphic, also the North American release of Xenosaga episode III had to edit 1 scene, ONE SCENE in order to prevent the ESRB from giving them an M. Also you have to realize the people that rate these don't even play the game, they are merely show video presentations of the content and they basically try to find anything and everything they view as questionable content.
In the end it's just about doing what it takes to get your game out, and it's not like it affects anything important, and it's not like the "uncensored" version is that hard to obtain (and costs less )